1. Field of the Invention
The invention relates to bleaching compositions and a method employing these compositions for cleaning substrates, especially fabrics, hard surfaces and dentures.
2. The Related Art
Many household and personal care products are formulated with a peroxygen material to effect removal of stain and soil. Typical materials which have been used in commerce are hydrogen peroxide, sodium perborate, sodium percarbonate, benzoyl peroxide, peracetic acid (generated through precursor compounds such as TAED) and persulfate (Oxone). Each of these has at least one important limitation. For instance, hydrogen peroxide, perborate and percarbonate require activating catalysts. Often the catalysts are expensive and in manufacturing environments may act as skin sensitizers. Instability is another problem with peroxygen materials. Peroxides are also aggressive against dyes resulting in color damaged substrates (e.g. fabrics). Considerable research has therefore been conducted to discover alternative bleaching systems.
Peroxynitrite is a free radical nitric oxide variant which has attracted considerable biochemical study. Free radical nitric oxide, .cndot.NO, an otherwise relatively toxic classified gas indirectly regulates the relaxation of vascular smooth muscle of blood cells in humans. It also plays an important role as a secondary messenger molecule in the nervous system. See R. F. Furchgott, J. V. Zawadzki, Nature (London), 1980, 288, 373; R. M. J. Palmer, A. G. Ferrige, S. Moncada, Nature, 1987, 327, 524; and L. J. Ignarro, G. M. Buga, K. S. Wood, R. E. Burns, G. Chaudhuri, Proc. Natl. Acad. Sci., USA, 1987, 84, 9265. An article by S. Moncada, R. M. J. Palmer, E. A. Higgs, Pharmacol. Rev., 1991 43, 109 reported generation of peroxynitrite in vivo from L-arginine by the enzyme .cndot.NO-synthase. The realization that .cndot.NO is generated in biological systems has led to an explosion of new research in physiology, pathology and pharmacology.
More recent investigations have shown that .cndot.NO reacts in a diffusion controlled reaction with super oxide, a reduced form of oxygen, to yield peroxynitrite. The latter is stable in alkaline solutions. See R. E. Huie, S. Padmaja, Free Rad. Res. Commun., 1993, 18, 195. Several experimental studies have employed peroxynitrite as an oxidizing agent for various inorganic and organic substrates. See A. M. Al-Ajlouni, E. S. Gould, Inorg. Chem., 1996, 35, 7892 and references cited therein. Lipid oxidation has also been investigated. Soybean phosphatidylcholine liposomes were oxidized to malondialdehyde and conjugated dienes, accompanied by oxygen consumption. However, no significant lipid peroxidation occurred above pH 9.5. See R. Radi, J. S. Beckman, K. M. Bush, B. A. Freeman, Arch. Biochem. Biophys., 1991, 288(2), 481.
Evident from the foregoing background information is that peroxynitrite has attracted considerable academic interest but few practical applications have been considered for this material.
Accordingly, it is an object of the present invention to provide another tool for the bleaching and cleaning of substrates, especially fabrics and household hard surfaces.
Another object of the present invention is to provide a bleaching composition effective at relatively low concentrations thereby achieving a cost effective stain removal system.
Still another object of the present invention is to provide a method for bleaching stained substrates such as clothes, household hard surfaces including dishes, tableware, sinks, toilets and the like, and even dentures.
Other objects of the present invention will become apparent through the following summary, detailed discussion and examples.